The purpose of this study is to evaluate the benefits of combined Glucotrol XL and acarbose therapy in patients with type II diabetes mellitus who cannot achieve adequate glycemic control with Glucotrol alone. The comparison of treatments will include evaluation of: fasting plasma glucose, post-prandial glucose excursions, incidence and frequency of hypoglycemia, free insulin, lipids, and overall metabolic control. This is a randomized, double-blinded, parallel controlled trial involving 26 patients with type II diabetes mellitus who are hyperglycemic on the maximum dose of a commercially-available sulfonylurea. Patients will undergo screening laboratory evaluations (including CBC with differential, UA, OP16, stimulated C-peptide in response to a mixed meal, lipoprotein profile, total insulin, HBA1c, EKG, fasting plasma glucose, and Beta HCG for females of reproductive age) and a brief interview to determine if they qualify for study participation. Patients who qualify will proceed to visit 2 at which time a history and physical examination will be conducted and the patients will be instructed in a 60% carbohydrate diet. At that time, patients will be switched to Glucotrol XL who are not already receiving it. Following a lead in period of 6 weeks, patients must have a fasting plasma glucose >140mg/dl on the maximum dose of Glucotrol XL (20mg/dl) and and a 60% carbohydrate diet in order to enter the study. The next visit (visit 3) will consist of an admission to the General Clinical Research Center (GCRC) at Duke University Medical Center at which time the following laboratory tests will be performed: fasting plasma glucose, HBA1c, C-peptide, total insulin, 1 hr post prandial insulin and glucose levels, 2 hr post prandial and glucose levels, and lipoprotein profile. During this admission, patients will be randomized to one of two treatment arms. One treatment will consists of therapy with Glucotrol XL and placebo for 4 months. The other treatment consists of 4 months of Glucotrol XL combined with acarbose therapy. The initial dose of acarbose will be 25 mg tid, increasing to 50 mg tid after 2 weeks and, if necessary, to 100 mg tid after an additional 2 weeks. Our end point will be a fasting plasma glucose under 120 mg/dl or maximum dose acarbose. Approximately 2 months following the admission, patients will return for visit 4 as an outpatient. The purpose of this visit is to assess the level of glucose control and to monitor for drug toxicity. Assessment will include examination of home blood glucose monitoring and the following labs: LFT's and HbAlc. Approximately 2 months after visit 4, patients will be readmitted to repeat the laboratory evaluations of the first admission.